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Question about using dual smoke stacks

 
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whall
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Joined: 13 Jan 2014
Posts: 281
Location: Rockwood, TN

PostPosted: Sat Aug 16 14 8:41 am    Post subject: Question about using dual smoke stacks Reply with quote

The way I have designed my cooker I am using a stack on each end.

I have used the pit calculator and it says I need roughly 36" of 6" ID pipe.

Will it create enough draft if I make them both 18"?

Or, Should I make them say 24" each? I'm thinking that making them both 36" will make too much draft

If I use dampers on the stacks could I get away with them being longer? I am thinking that if I make them short It will look weird on such a big cooker
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SoEzzy
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Joined: 13 Oct 2006
Posts: 13183
Location: SLC, UT

PostPosted: Sat Aug 16 14 9:28 am    Post subject: Re: Question about using dual smoke stacks Reply with quote

whall wrote:
The way I have designed my cooker I am using a stack on each end.

I have used the pit calculator and it says I need roughly 36" of 6" ID pipe.


That's the total length with one exhaust stake.

Quote:
Will it create enough draft if I make them both 18"?


Yes it will, as 2 x 18 = 36

Quote:
Or, Should I make them say 24" each? I'm thinking that making them both 36" will make too much draft


I'd go with 24" if you intend to have dampers, at 24" you could run them 25% closed and still have nearly the same flow as 18".

Quote:
If I use dampers on the stacks could I get away with them being longer? I am thinking that if I make them short It will look weird on such a big cooker


That's always a consideration, but run it at a sensible length and when you cook on it you will learn how it cooks, you could theoretically put 2 x 36" stacks on it with dampers on both, and run both at 50% closed to equal 1 x 36" exhaust.

JM2C!
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k.a.m.
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Joined: 12 Dec 2007
Posts: 26016
Location: Southeast Texas.

PostPosted: Sun Aug 17 14 9:36 pm    Post subject: Reply with quote

whall, your firebox is mounted underneath your cooker with your heat/smoke traveling up not across, the calculator figures cookers with horizontal draft.
In my opinion you can use the two 18" exhausts, I would definitely have to dampers on the top of them if nothing more than to close off the cooker and keep critters out when not in use.
I would try to use the cooker several cooks with them wide open to see how she cooks using just the intake for temp control.
I hope this helps. Very Happy
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TrailerBuilder
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Joined: 08 Feb 2010
Posts: 3151
Location: Springfield MO

PostPosted: Sun Aug 17 14 11:13 pm    Post subject: Reply with quote

On my backyarder, 20"x42" the calculator called for 44" of 3" pipe, so that came out to 22" per side. I went with 33" stacks on each side to make the stacks match up with the looks of the cooker. With the longer stacks, it draws just fine. I run my stacks wide open and adjust the intake to control my heat. Works great that way. Basically, I would get the minimum amount of stack needed in whatever you decide, but I would make the final lengths what ever looks best on the cooker and appeals to you.

JM2CW
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whall
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Joined: 13 Jan 2014
Posts: 281
Location: Rockwood, TN

PostPosted: Mon Aug 18 14 9:23 pm    Post subject: Reply with quote

SoEzzy Thanks for the math lesson Laughing I was unsure of how having two stacks instead of just one would affect the draft. I guess I was over thinking it Embarassed

k.a.m. I was planning on having dampers like you said if nothing else to keep the critters out or in depending on the situation Laughing

TrailerBuilder Thanks for sharing your experience Smile

I guess I will get a couple pieces of scrap lumber and cut them to different lengths to give me an idea of how they will look.

Thanks for the help!
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az mike
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Joined: 13 Nov 2008
Posts: 382
Location: seaz

PostPosted: Mon Aug 25 14 7:30 pm    Post subject: Reply with quote

This last cooker that I built is using one center exhaust but it exits from a small cook chamber on top of the main box. The fire box is only fed air from a 110v fan and closed for most cooks. The damper is on the fan that controls air intake. This is the absolute most control I have ever had in a smoker. I burn only seasoned pecan wood and use far less wood. I like to cook poultry hot and can cook at 300 and have the skin still soft and not too smokey flavored. I also like to cook peppers hot and fast. I would recommend air induction on a build, my sons call it "turbo charged"!
Anyway, I have one 6" dampered exhaust that exits through a second small cook chamber on top of the main box. This mini cooker has a couple lazy susan rotating screens for chilis and dogs etc. Temps are very much the same in the main box and little one. Mike
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